With the emergence and popularity of various types of smart electronic equipment, earphones have become more important accessories for electronic equipment in people's daily lives. Noisy environments can interfere with the quality of the sound received through earphones. Some people who are especially affected are business people who frequently travel by air, people who commute on crowded subway trains and buses, as well as people who work inside air-conditioned rooms. Therefore, there is a rapidly growing demand for noise canceling earphones.
ANC (Active Noise Cancelation) earphones are a type of noise canceling earphones, and unlike standard earphones, include a noise canceling circuit for canceling noise in addition to an earphone plug and an audio playback unit. The noise canceling circuit typically requires power from a dedicated power source in order to sufficiently power it. The power source usually contains a battery, a voltage converter, and a regulator circuit. When compared to standard earphones (e.g., non-ANC earphones), these components increase the size, weight, and cost of ANC earphones. Further, the battery voltage of typical battery cells is generally not suitable for directly driving the noise canceling circuits. The noise canceling circuit further needs to comprise a DC-to-DC (direct current to direct current) voltage conversion circuit to regulate and stabilize the battery voltage to reach the suitable operating voltage range of the noise canceling circuit. The noise canceling circuit structurally complicates earphones by requiring earphones to have more components; the noise canceling circuit further complicates earphone mass production by increasing earphone sizes, weights, and production costs.
Among the prior art, there is a method of directly using an electronic equipment's power source to supply power to a noise canceling earphone. This method configures a power pin receptacle of an electronic equipment's earphone jack, configures a power pin of a noise canceling earphone's earphone plug, and supplies power from the power source of the electronic equipment through the coupling between the earphone jack's power pin receptacle and the earphone plug's power pin to a noise canceling circuit of the earphone. This method requires both the earphone plug and earphone jack to have a specific structural configuration, namely a 5-pole configuration. In order to achieve noise cancelation, the 5-pole earphone plug and the 5-pole earphone jack must be used together. This restricts the compatibility between noise canceling earphones and electronic equipment.